Examination of the accessory tendons of extensor hallucis longus muscle in fetuses.

There are various data about the incidence of accessory tendons (AT) of extensor hallucis longus (EHL) muscle; however, their function is unknown. This study aimed to determine the incidence and morphometric features of the AT of EHL muscle in fetuses in order to provide more information to discuss its possible function. Forty-five fetuses (26 female and 19 male) were used in this study. Fetuses were grouped as Group A (16-21 weeks), Group B (22-27 weeks), and Group C (28-34 weeks) according to their age. In 23 (51%) out of 45 fetuses, there were AT. These were bilateral in 15 fetuses (65%) and unilateral in eight fetuses (35%). Fifty-two percent of the fetuses in group A, 43% in group B, and 67% in group C had AT. AT were observed in 14 female (54%) and 9 male (47%) fetuses. In all cases, the AT were always diverging to the medial side of the main EHL tendons and attached to the metatarsophalangeal joint capsule distal to the joint space. Significant correlations were observed in this study between EHL and AT widths as well as between EHL width and EHL-AT distance on both sides. The present study is the first to provide morphometric data about the AT of EHL muscle in fetuses which will be of use in understanding their function, particularly in biomechanics of the great toe. (c) 2008 Wiley-Liss, Inc.